Methods for transferring a useful layer of silicon carbide to a receiving substrate

ABSTRACT

Methods for transferring a useful layer of silicon carbide to a receiving substrate are described. In an embodiment, the invention relates to a method for recycling of a silicon carbide source substrate by removal of the excess zone followed by a finishing step to prepare the source substrate for recycling and reuse. Preferably, the excess zone is removed by a thermal budget where the temperature and time of such treatment causes exfoliation of the excess zone. The finishing step is performed in a manner to provide the desired surface roughness for the substrate so that it can be recycled for re-use. The technique includes implanting at least H +  ions through a front face of a source substrate of silicon carbide with an implantation energy E greater than or equal to 95 keV and an implantation dose D chosen to form an optimal weakened zone near a mean implantation depth, the optimal weakened zone defining the useful layer and a remainder portion of the source substrate. The method also includes bonding the front face of the source substrate to a contact face of the receiving substrate, and detaching the useful layer from the remainder portion of the source substrate along the weakened zone while minimizing or avoiding forming an excess zone of silicon carbide material at the periphery of the useful layer that was not transferred to the receiving substrate during detachment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 10/893,192 filedJul. 15, 2004 now U.S. Pat No. 6,974,760, which is a continuation ofInternational application no. PCT/EP03/00692 filed Jan. 21, 2003, theentire content of each of which is expressly incorporated herein byreference thereto.

BACKGROUND ART

The present invention relates to an optimized method for transferring anuseful layer of monocrystalline silicon carbide (SiC) derived from asource substrate of the same material to a receiving or stiffeningsubstrate. The method permits recycling of the substrate after thetransfer of the thin useful layer.

The method known under the trademark “SMART-CUT®” enables a thin layerto be transferred from a source substrate to a receiving substrate suchas, for example, an oxidized silicon or polycrystalline silicon carbidesubstrate. This method also enables the source substrate from which thethin layer has been taken to be reused. However, after each layertransfer step, the upper surface of the source substrate has a certainnumber of surface irregularities. The formation of these surfaceirregularities will be described with reference to FIGS. 1-5, which showa specific example of implementation of the “SMART-CUT®” method. Thismethod is known to those skilled in the art and will not be described indetail.

FIG. 1 shows a source substrate 1 which has a planar face 2, or a “frontface”, through which gas species have been implanted. This implantationis carried out by ion bombardment, for example with H⁺ ions (reference Bin FIG. 1) using an implanter. The implantation is performed at aspecific energy, implantation dose, and temperature, and creates aweakened zone 3 in the neighborhood of the mean implantation depth p ofthe ions. This weakened zone 3 delimits two portions in the sourcesubstrate 1: an upper thin layer or useful layer 100 extending betweenthe front face 2 and the weakened zone 3, and the remainder 10 of thesubstrate. As shown in FIG. 2, a stiffener or receiving substrate 4 isthen applied to the front face 2 of the source substrate 1. Thisstiffener is chosen by a person skilled in the art as a function of thefinal application envisaged. The receiving substrate 4 may be applied ina known manner, for example, by evaporation, spraying, chemical vapordeposition, or it can be bonded to the front face by using an adhesiveor by a technique known as “bonding by molecular adhesion”, also knownas “wafer bonding”.

As shown in FIG. 3, the thin layer 100 is detached from the remainder 10of the substrate 1. This detachment step, which is symbolized by thearrows S, may be performed by applying either mechanical stresses to thestiffener 4, or by the applying thermal energy to the assembly thatincludes the stiffener 4 and the substrate 1.

Wafers chosen for use as a source substrate 1 possess reduced edges dueto chamfering operations performed, for example, during theirmanufacture. As a result, the adhesion forces between the stiffener 4and the front face 2 are weaker in a substantially annular periphery ofthe source substrate 1. Consequently, when the stiffener 4 is detachedfrom the source substrate 1, only the central portion of the thin layer100, which is strongly adhering to the stiffener 4, is detached, whilethe substantially annular periphery of the useful layer 100 remainsattached to the remainder 10 of the source substrate 1 as shown in FIG.3. As a result, the source substrate 1 thus simultaneously includes asurface roughness 11 in its central portion due to detachment in theregion of the weakened zone 3, and at its periphery has an excessthickness 12 or surface topology in the form of a blistered zonecorresponding to the zones that were not transferred to the receivingsubstrate or stiffener 4. The depth of this excess zone 12 is equal tothe thickness of the transferred thin layer 100. It typically variesfrom several tens of nanometers to more than a micrometer. The depth isdetermined by the implantation energy of the hydrogen ions.

In FIGS. 3 and 4, the excess zone 12 has intentionally been shown, forthe sake of clarity and simplification, having a rectangular crosssection and having a noticeable thickness with respect to the remainder10 of the source substrate. In reality, it has a much more irregularshape and a proportionally smaller thickness.

Before proceeding to transfer another thin layer, it is imperative torecycle the remainder 10 of the source substrate. This recyclingconsists of a planarization step, depicted by the arrows P in FIG. 4,wherein the excess zone 12 is eliminated, and a specific finishing stepdepicted by the arrow F in FIG. 5, that permits elimination of thesurface roughness 11 to attain a substrate having a new front face 2′.These recycling steps are generally performed by mechanical and/ormechanical-chemical polishing techniques. In the specific case where thesource substrate 1 is made of silicon carbide, an extremely hardmaterial, such polishing steps are extremely long and costly.

The prior art document, “The effects of damage onhydrogen-implant-induced thin-film separation from bulk siliconcarbide”, R. B. Gregory, Material Research Society Symposium, Vol. 572,1999, discloses that the choice of hydrogen implantation conditions forimplanting into silicon carbide permits varying the percentage ofremoval of the excess zone, that is, the percentage of the free surfaceof silicon carbide which is spontaneously eliminated during thermalannealing of the substrate. In this article, the results show the H⁺ ionimplantation dose as a function of the percentage of the excess zoneremoved is a bell-shaped curve at an implantation energy of 60 keV, witha maximum value of 33% of the zone removed, for an implantation dose of5.5×10¹⁶ H⁺/cm². When departing from this value, that is if theimplantation dose is increased or decreased, then the removal percentagedecreases.

The document “Complete surface exfoliation of 4H—SiC by H⁺ and Si+co-implantation”, J. A. Bennett, Applied Physics Letters, Vol. 76, No.22, pages 3265-3267, May. 29, 2000, describes that it is possible toperform a complete exfoliation of the surface of a silicon carbidesubstrate by co-implanting H⁺ and Si⁺ ions. More specifically, thisdocument describes tests performed on 4H—SiC silicon carbide byimplanting Si⁺ ions at various doses and at an energy of 190 keV, thenimplanting H⁺ ions at an implantation dose of 6×10¹⁶ H⁺/cm² and at anenergy of 60 keV. Implantation doses of Si+ greater than or equal to5×10⁵ Si⁺/cm² permitted exfoliation of 100% of the silicon carbidesurface. However, the Si ion implantation dose necessary for totalexfoliation of the SiC layer is also high enough to render the siliconcarbide amorphous. This method is therefore incompatible withtransferring a thin film of silicon carbide of good crystalline quality,since it is not possible to utilize a thin film from such a substratefor forming devices used in microelectronics or opto-electronics.

SUMMARY OF THE INVENTION

Presented are methods for transferring a useful layer of silicon carbideto a receiving substrate. One embodiment of the invention relates to amethod for recycling of a silicon carbide source substrate by removal ofthe excess zone followed by a finishing step to prepare the sourcesubstrate for recycling and reuse. Preferably, the excess zone isremoved by a thermal budget where the temperature and time of suchtreatment causes exfoliation of the excess zone. The finishing step isperformed in a manner to provide the desired surface roughness for thesubstrate so that it can be recycled for re-use.

This technique includes implanting at least H⁺ ions through a front faceof a source substrate of silicon carbide with an implantation energy Egreater than or equal to 95 keV and an implantation dose D chosen toform an optimal weakened zone near a mean implantation depth, theoptimal weakened zone defining the useful layer and a remainder portionof the source substrate. The method also includes bonding the front faceof the source substrate to a contact face of the receiving substrate,and detaching the useful layer from the remainder portion of the sourcesubstrate along the weakened zone while minimizing or avoiding formingan excess zone of silicon carbide material at the periphery of theuseful layer that was not transferred to the receiving substrate duringdetachment. Such a method facilitates recycling the remainder portion ofthe source substrate.

In a preferred embodiment, the implantation dose D of H⁺ ions, expressedas a number of H⁺ ions/cm², satisfies the equation:[(E×1×10¹⁴+5×10¹⁶)/1.1]≦D≦[(E×1×10¹⁴+5×10¹⁶)/(0.9)]. Advantageously, theimplanted ions include H⁺ ions, or a combination of H⁺ ions and heliumor boron ions. The method beneficially includes implanting H⁺ ions whilemaintaining the source substrate at a temperature no greater than 200°C. Ions may be implanted in a random fashion. The source substrate maybe a disoriented monocrystalline silicon carbide.

An advantageous implementation further includes detaching the usefullayer along the optimal weakened zone by applying a thermal budget orexternal mechanical stresses and in a manner so that no excess zoneremains. In a beneficial implementation, the useful layer is detached byapplying a thermal budget that is greater than about 700° C.

Another advantageous embodiment includes providing a layer of amorphousmaterial on the source substrate before implanting ions, wherein thethickness of the amorphous material is less than or equal to about 50nanometers. The amorphous material may be formed of a material chosenfrom among silicon oxide (SiO₂) or silicon nitride (Si₃N₄). In avariant, the bonding step includes molecularly adhering the receivingsubstrate to the front face of the source substrate. An intermediatebonding layer may be provided on at least one of the front face and thecontact face, and the intermediate bonding layer could include anamorphous material such as silicon oxide (SiO₂) or silicon nitride(Si₃N₄).

In a preferred embodiment, the receiving substrate comprises at leastone of silicon, silicon carbide, gallium nitride, aluminum nitride,sapphire, indium phosphide, gallium arsenide, or germanium. Inparticular, the receiving substrate may be made of silicon with a lowoxygen content. Such a receiving substrate may be provided by using azone melting growth method.

Beneficially, the method also includes finishing a front face of theremainder of the source substrate after detachment occurs, for use insubsequent bonding operations.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, purposes and advantages of the invention will becomeclear after reading the following detailed description with reference tothe attached drawings, in which:

FIGS. 1-5 are diagrams showing the different steps of a method oftransfer of a thin silicon carbide layer according to the prior art;

FIGS. 6-18 are diagrams showing the steps of alternative methodsaccording to the invention;

FIG. 19 is a graph showing the exfoliated zone percentage, or thepercentage of the excess zone removed as a function of the H⁺ ionimplantation dose D, at various implantation energies; and

FIG. 20 is a graph showing the values of H⁺ ion implantation energy E asa function of the H⁺ ion implantation dose D to obtain 100% exfoliationor removal of the thin layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The methods according to the invention will now be described withreference to FIGS. 6-18. FIGS. 6-18 are similar to FIGS. 1-5, andidentical elements have the same reference numerals.

Referring to FIG. 6, a goal of the invention is to optimize theimplantation conditions B of atomic species within a source substrate 1of monocrystalline silicon carbide. In particular, it is desired tocreate an “optimal weakened zone” 5 in the neighborhood of the meandepth p of ion implantation, so that it is possible to remove orexfoliate, after the useful layer 100 is detached and after anappropriate thermal budget is applied, 100% or substantially about 100%of the blistered excess zone 12 which remained integral to the remainder10 of the source substrate in the prior art (see FIG. 3). “Optimallyweakening” means introducing atomic species into the crystal in aprecise and controlled manner in order to optimally activate theweakened mechanisms used. The implantation of atomic species consists ofbombarding the front face 2 of the substrate 1 with H⁺ ions, andpossibly jointly bombarding with H⁺ ions and helium or boron ions,wherein the H⁺ ions nevertheless remain in the majority. Theimplantation of these ions through the surface of the monocrystallinesilicon carbide source substrate 1 is performed using an ion beamimplanter.

Various tests were conducting concerning implanting ions through thesurface of a silicon carbide source substrate 1 in order to determinethe best operating conditions. As illustrated in FIGS. 7 and 8, whichshow the crystalline structure of silicon carbide, the implantation B ofions is always performed perpendicularly to the planar surface 2 of thesource substrate 1. The case illustrated in FIG. 7 corresponds to anoriented silicon carbide crystal (known to those skilled in the art bythe term “on axis”), wherein the stacking of silicon and carbon atomsare situated in a plane parallel to the upper planar surface or frontface 2. The ions then penetrate parallel to the crystal growth axis C ofthe crystal. In contrast, the case illustrated in FIG. 8 corresponds toa disoriented silicon carbide crystal (known to those skilled in the artby the term “off axis”), wherein the stacking of silicon and carbonatoms are situated in a plane which is not parallel to the front face 2,but which forms an angle α with the latter. The ions then penetratealong an axis perpendicular to the front face 2 but angularly offsetfrom the crystal growth axis C by the value of this angle α. Thedisorientation of the crystal is obtained in an artificial fashion,generally by cutting the crystal. The angle α can have different values,but is 3.5°, 8°, or 15° in current commercially available crystals ofsilicon carbide.

In the two cases shown in FIGS. 7 and 8, microcavities 50 are formed asa result of ion implantation in a plane that is perpendicular to thecrystalline growth axis C. Consequently, in the oriented crystal of FIG.7, the microcavities 50 are parallel to the front face 2 and form anoptimal weakened zone 5 that is parallel to the plane of the front face2. This optimal weakened zone 5 is a substantially continuous fractureline. In contrast, in the disoriented crystal shown in FIG. 8, themicrocavities 50 are inclined with respect to the plane of the frontface 2 and do not form a continuous line.

It has been observed experimentally that for a given implantation dose Dand energy E, a greater weakening of the zone 5 is obtained whenimplantation is performed on a disoriented crystal. For laterprocessing, such an optimized weakened zone results in an improvement inthe exfoliation percentage of the excess zone 12 (shown in FIG. 3). Inan advantageous manner, such ion implantation is performed in a randomfashion, to avoid the phenomenon termed “channeling.” The channelingphenomenon occurs when ions are implanted along specific channels orcrystallographic axes. The ions thus introduced encounter fewer atoms ontheir trajectories, resulting in fewer interactions and less braking ofthe ions. These ions will therefore be implanted deeper. The processaccording to the invention seeks to avoid this channeling phenomenon forindustrial reasons, because channeled implantation is not anindustrially feasible technique.

Furthermore, in order to improve the percentage of exfoliation obtainedduring detachment, and to operate in a random implantation mode, it ispreferable (but not obligatory) to perform ion implantation through alayer of amorphous material 20 that has been formed on the front face 2of the source substrate 1. This alternative embodiment is shown in FIG.9. The layer of amorphous material 20 is advantageously a layer ofsilicon oxide (SiO₂) or of silicon nitride (Si₃N₄). However, it shouldnot exceed a thickness of about 50 nm (5×10⁻⁹ m), at the risk ofmodifying the relationship connecting the implantation energy E and theimplanted dose D as will be defined below.

Finally, the tests performed showed that ion implantation shouldpreferably be preformed without external heat supplied, so that it is ata maximum temperature of about 200° C., wherein the implantation is ableto bring the silicon carbide substrate substantially to thistemperature. If the substrate is heated during implantation, for exampleto temperatures markedly greater than 650° C., degradation orsuppression of the macroscopic exfoliation phenomenon is observed. Thiscan be explained by the activation during implantation of diffusion andrecrystallization mechanisms which participate in the process. Thisactivation in situ, which is not controlled, degrades the control of thedesired exfoliation or removal effect. Other, complementary tests wereconducted to determine the best pairs of implantation dose D andimplantation energy E to be used. These trials will be described indetail below.

Referring to FIG. 10, the receiving substrate 4 is next bonded to thefront face 2 of the source substrate 1. The substrate 4 isadvantageously bonded to the front face 2 by molecular adhesion, sincethis is the mode of bonding best suited to electronic applications, andbecause of the homogeneity of the bonding forces used and of thepossibility of bonding together numerous materials of different natures.However, bonding could likewise be performed by other known prior arttechniques. Bonding can be performed by contacting one of the contactfaces 40 of the receiving substrate 4 to the front face 2 of the sourcesubstrate 1, either directly (see FIG. 10) or by means of one or moreintermediate bonding layers 6 deposited on the contact face 40 of thesubstrate 4 (as shown in FIG. 11), or onto these two faces. Theseintermediate bonding layers 6 may be insulating layers, for example, ofsilicon oxide (SiO₂) or silicon nitride (Si₃N₄), or may be conductivelayers. It should noted that when the implantation B is performedthrough a layer of amorphous material 20, the latter can then play thepart of an intermediate bonding layer 6. As a result, an assembly oflayers as illustrated in FIGS. 12 and 13, respectively, is obtained.

The receiving substrate is advantageously (but not obligatory) chosenfrom silicon, silicon carbide, gallium nitride (GaN), aluminum nitride(AlN), sapphire, indium phosphide (InP), gallium arsenide (GaAs), orgermanium (Ge). Other materials can likewise be used. The receivingsubstrate can likewise be a fragile or weakened substrate, such assilicon obtained by zone fusion growth, with a low oxygen content, suchas monocrystalline silicon obtained by the zone fusion method startingfrom polycrystalline silicon.

Referring to FIG. 14, the receiving substrate 4 and the thin layer 100are then detached (arrows “S”) from the remainder 10 of the sourcesubstrate 1. Detachment S can be performed either by application ofexternal mechanical stresses, or by a thermal treatment with anappropriate thermal budget (see FIG. 17). In a manner known to thoseskilled in the art, the external mechanical stresses can be, forexample, the application of shear, traction, or compression forces, orthe application of ultrasound, or of an electrostatic or electromagneticfield. If the detachment S is performed using external mechanicalstresses, an annealing treatment then follows according to anappropriate thermal budget to completely, or almost completely,exfoliate or remove the excess zone 12 of the thin layer 100 from thesource substrate 1. This excess zone remained integral to the sourcesubstrate 1 (see FIG. 14) and did not bond to the receiving substrate 4so it is removed (see FIG. 15). The thermal budget corresponds to theproduct of the annealing treatment temperature and the duration of thistreatment. Such a treatment is simpler and quicker to use than thepolishing used in the prior art. Lastly, a finishing step F of thesource substrate 1 may be conducted (see FIG. 16). This finishing stepis for eliminating the surface roughness 11. It is generally performedby mechanical-chemical polishing. The free surface of the thin layer 100can likewise be finished.

If the detachment S of the thin layer 100 from the remainder 10 of thesource substrate 1 is performed by a thermal annealing treatment (seeFIG. 17), a complete or substantially complete exfoliation or removal ofthe excess zone 12 then simultaneously occurs (see FIG. 18). Inpractice, such an application of heat causes the defects ormicrocavities 50 to grow until they form micro-cracks 51 which, whenconnected together, result in a cleavage plane and in detachment alongthe optimal weakened zone 5. An optional finishing step F is thenperformed, as illustrated in FIG. 16.

The tests used to determine the best pairs of values of implantationdose D and implantation energy E of H⁺ ions will now be described. Inparticular, the tests were conducted under the following operatingconditions. H⁺ ion implantation was performed on the front face of amonocrystalline silicon carbide SiC₄H substrate disoriented by 8° (knownto those skilled in the skilled in the art as “4H—SiC8°off-axis”),covered with an amophous layer of silicon oxide about 50nanometers (50 nm) thick. The implantation temperature was below 200.degree. C. Four series of tests were performed with implantationenergies E of respectively 50 keV, 95 keV, 140 keV and 180 keV. For eachvalue of energy E, the implantation dose D was varied between5.25×10¹⁶H⁺/cm² and 8×10¹⁶H⁺/cm². A receiving substrate 4 made ofsilicon was then applied to the source substrate 1, and annealing wasthen performed at 900° C. for 1 hour. The percentage of the peripheralzone 12 that was removed or exfoliated, which in the prior art remainedintegral with the remainder 10 of the substrate, was then measured. Theresults obtained are given in the following Table wherein a value of100% means that the entire excess zone 12 which is not in intimatecontact (that is, has not adhered) to the receiving substrate 4 isremoved. A value of 30%, for example, means that only 30% of the excesszone 12 was removed, and that 70% of the excess zone 12 remainedintegral with the remainder 10 of the substrate 1.

Implantation Implantation dose D (10¹⁶ H⁺/cm²) Energy E (keV) 5.25 5.55.75 6 6.5 6.75 7 7.25 7.5 8 Exfoliated 50 5 50 15 Zone 95 10 100 60 30(%) 140 40 80 100 60 40 180 30 90 100 80 40

Tests conducted with implantation energies less than 50 keV did not givegood removal results. The results obtained above have also been graphedin FIG. 19. As shown, for each implantation energy B value greater thanor equal to 95 keV, there is an implantation dose value D which enables100% removal of the excess zone to be obtained (bell-shaped curvesobtained).

FIG. 20 is a graph showing the H+ ion implantation dose D as a functionof the implantation energy E of these same ions to obtain 100% removalor exfoliation of the excess zone. The straight line obtainedcorresponds to the following equation:D=E×1.10¹⁴+5.10¹⁶  (1)with E≧95 keV, in which the H+ ion implantation energy E is expressed inkeV and the implantation dose D of these ions is expressed in H+ions/cm².

Taking into account any fluctuations of the values of D and E connectedto possible slight experimental variations and to manufacturingtolerances and control of the implantation apparatus used, it has beendiscovered that the pair of values (of D and B) should obey thefollowing equation:−ε×D≦D−(E×1×10¹⁴+5×10¹⁶)≦ε×D   (2)

where D and E have the aforementioned meanings and where ε×D representsthe absolute tolerance for a given value of E between the theoreticalvalue of D obtained according to the above Equation (1) and anacceptable value of D, and where ε represents the relative tolerance.After experimentation, it was considered that this relative tolerance εwas equal to 10%.

The following equation (3) results from this:−0.1×D≦D−(E×1×10¹⁴+5×10¹⁶)≦0.1×D   (3)which can also be expressed as the following equation (4):[(E×1×10¹⁴+5×10¹⁶)/1.1]≦D≦[(E×1×10¹⁴+5×10¹⁶)/(0.9)]  (4)

The pairs of values of D and E which obey the above equation (4) permitan optimal weakening of the weakened zone 5 to be obtained, and afterhaving applied a sufficient thermal budget, permits complete or almostcomplete removal of the excess zone 12, which is the portion of theuseful layer that has not been transferred to the receiving substrate 4.

Supplementary tests were then performed to determine the appropriatethermal budget. Below 700° C., the mechanisms of diffusion of hydrogenwithin the SiC material are practically inoperative. It was thuspossible to determine that the thermal budget necessary for complete oralmost complete removal or exfoliation of the excess zone 12 should beabove about 700° C. and preferably above about 800° C. The resultobtained therefore, is a thin layer 100 of SiC of good crystallinequality, and a source substrate 1 having a front face 11 which is freefrom surface topologies or an excess zone 12.

1. A method for recycling a SiC source substrate, which comprises:implanting at least H⁺ ions through a front face of a source substrateof silicon carbide with a selected combination of an implantation energyE and an implantation dose D of H⁺ ions sufficient to form an optimalweakened zone, with the optimal weakened zone defining a useful layercomprising silicon carbide and a reminder portion of the sourcesubstrate; bonding the front face of the source substrate to a contactface of a receiving substrate; detaching the useful layer from theremainder portion of the source substrate along the weakened zone, thedetaching comprising applying a thermal budget, and removing an excesszone by exfoliation; wherein the optimal weakened zone produced by theselected combination of implantation energy and dose is sufficient tocause exfoliation of at least about 80% of the peripheral excess zone ofsilicon carbide to facilitate recycling of the remainder portion of thesource substrate by minimizing or avoiding forming an excess zone ofsilicon carbide material at the periphery of the useful layer that wasnot transferred to the receiving substrate during detachment.
 2. Themethod of claim 1 wherein the implantation dose D of H⁺ ions, expressedas a number of H⁺ ions/cm², satisfies the equation:[(Ex1×10¹⁴+5×10¹⁶)/1.1]≦D≦[(Ex1×10¹⁴+5×10¹⁶)/(0.9)].
 3. The method ofclaim 1, wherein the implanted ions comprise H⁺ ions, a combination ofH⁺ ions and helium ions or a combination of H⁺ ions and boron ions.
 4. Amethod for recycling a SiC source substrate, which comprises: implantingat least H³⁰ ions through a front face of a source substrate of siliconcarbide with a selected combination of an implantation energy E and animplantation dose D of H⁺ ions sufficient to form an optimal weakenedzone, with the optimal weakened zone defining a useful layer comprisingsilicon carbide and a remainder portion of the source substrate, andwith the implanting conducted while maintaining the source substrate ata temperature that is no greater than 200° C.; bonding the front face ofthe source substrate to a contact face of a receiving substrate;detaching the useful layer from the remainder portion of the sourcesubstrate along the weakened zone, the detaching comprising applying athermal budget, removing an excess zone by exfoliation; and wherein theoptimal weakened zone produced by the selected combination ofimplantation energy and dose facilitates recycling the remainder portionof the source substrate by minimizing or avoiding forming an excess zoneof silicon carbide material at the periphery of the useful layer thatwas not transferred to the receiving substrate during detachment.
 5. Themethod of claim 1, wherein the source substrate comprises a disorientedmonocrystalline silicon carbide.
 6. The method of claim 1, which furthercomprises detaching the useful layer along the optimal weakened zone byapplying a thermal budget or mechanical stresses in a manner so that noexcess zone remains.
 7. The method of claim 6, wherein the useful layeris detached by applying a thermal budget at a temperature that isgreater than about 700° C.
 8. The method of claim 1, which furthercomprises implanting ions in a random fashion.
 9. The method of claim 1,which further comprises providing a layer of amorphous material on thesource substrate before implanting ions, wherein the thickness of theamorphous material is less than or equal to about 50 nanometers.
 10. Themethod of claim 9, wherein the amorphous material is formed of siliconoxide or silicon nitride.
 11. The method of claim 1, wherein the bondingstep comprises molecularly adhering the receiving substrate to the frontface of the source substrate.
 12. The method of claim 11, which furthercomprises providing an intermediate bonding layer on at least one of thefront face and the contact face.
 13. The method for fecycling a Sicsource subsrate, which comprises: implanting at least H⁺ ions through afront face of a source substrate of silicon carbide with an implantationenergy E greater than or equal to 95 keV and an implantation dose D ofH⁺ ions sufficient to form an optimal weakened zone near a meanimplantation depth, with the optimal weakened zone defining a usefullayer and a remainder portion of the source substrate; providing anintermediate bonding layer comprising an amorphous material on at leastone of the front face of the source substrate and a contact face of areceiving substrate; bonding the front face of the source substrate to acontact face of the receiving substrate, wherein the bonding stepcomprises moleculary adhering the receiving substrate to the front faceof the source substrate; detaching the useful layer from the remainderportion of the source substrate along the weakened zone while minimizingor avoiding forming an excess zone of silicon carbide material at theperiphery of the useful layer that was not transferred to the receivingsubstrate during detachment, to thus facilitate recycling the remainderportion of the source substrate; applying a thermal budget that isappropriate to remove the excess zone from the surface of the remainderportion of the source substrate, and eliminating source substratesurface roughness via a finishing step to prepare the source substratefor recycling and reuse.
 14. The method of claim 13, wherein theamorphous material is silicon oxide or silicon nitride.
 15. the methodof claim 13, wherein the receiving substrate comprises at least one ofsilicon, silicon carbide, gallium nitride, aluminum nitride, sapphire,indium phosphide, gallium arsenide, and germanium.
 16. The method ofclaim 1, wherein the receiving substrate comprises silicon having a lowoxygen content.
 17. The method of claim 1, further comprising providinga finished front face of the remainder of the source substrate afterdetachment for use in subsequent bonding operations.
 18. A method forrecycling a SiC source substrate, which comprises: implanting at leastH⁺ ions through a front face of a source substrate of silicon carbidewith an implantation energy E greater than or equal to 95 keV and animplantation dose D of H⁺ ions sufficient to form an optimal weakenedzone near a mean implantation depth, with the optimal weakened zonedefining a useful layer and a remainder portion of the source substrate;bonding the front face of the source substrate to a contact face of areceiving substrate; detaching the useful layer from the remainderportion of the source substrate along the weakened zone by heating thesource substrate/receiving substrate assembly to a temperature of above700° C. until the useful layer detaches while minimizing or avoidingforming an excess zone of silicon carbide material at the periphery ofthe useful layer that was not transferred to the receiving substrateduring detachment, to thus facilitate recycling the remainder portion ofthe source substrate; and applying a thermal budget that is appropriateto remove the excess zone from the surface of the remainder portion ofthe source substrate, eliminating source substrate surface roughness viaa finishing step to prepare the source substrate for recycling andreuse.
 19. The method of claim 18 wherein the useful layer is detachedby heating the source substrate/receiving substrate assembly to atemperature of above 800° C. until the useful layer detaches.
 20. Themethod of claim 1 wherein the useful layer is detached while minimizingformation of an excess zone of silicon carbide material at the peripheryof the useful layer that was not transferred to the receiving substrateduring detachment.
 21. The method of claim 1 wherein the useful layer isdetached while completely avoiding formation of an excess zone ofsilicon carbide material at the periphery of the useful layer that wasnot transferred to the receiving substrate during detachment.
 22. Amethod for recycling a SiC source substrate, which comprises: implantingat least H⁺ ions through a front face of a source substrate of siliconcarbide with an implantation energy E greater than or equal to 95 keVand an implantation dose D of H⁺ ions sufficient to form an optimalweakened zone near a mean implantation depth, with the optimal weakenedzone defining a useful layer and a remainder portion of the sourcesubstrate; bonding the front face of the source substrate to a contactface of a receiving substrate; detaching the useful layer whichcomprises monocrystalline silicon carbide 4H—SiC material from theremainder portion of the source substrate along the weakened zone whileminimizing or avoiding forming an excess zone of silicon carbidematerial at the periphery of the useful layer that was not transferredto the receiving substrate during detachment, to thus facilitaterecycling the remainder portion of the source substrate; and applying athermal budget that is appropriate to remove the excess zone from thesurface of the remainder portion of the source substrate, eliminatingsource substrate surface roughness via a finishing step to prepare thesource substrate for recycling and reuse.
 23. The method of claim 1wherein the implantation energy is greater than or equal to 95 keV. 24.The method of claim 1 wherein the detaching further comprises applyingexternal mechanical stresses.
 25. The method of claim 12, wherein theintermediate bonding layer comprises an amorphous material.
 26. Themethod of claim 1 wherein the thermal budget comprises heating thesource substrate/receiving substrate assembly to a temperature of above700° C. until the useful layer detaches.
 27. The method of claim 1wherein the useful layer is provided by a monocrystalline siliconcarbide 4H—SiC material.